How are you defining notional here?
To my knowledge it would be:
[# of contracts (long or short)] x [point value] x [strike]
However, that appears to be a somewhat abstract risk measure. Not a criticism, I'm genuinely curious and feel that I'm missing something. Thanks.
pretty much how it's calculated. The way I look at it is the maximum theoretical delta you can have (so a straddle counts the same as a naked option).
That represents an upper bound on your risk and it most closely equates your position to a long/short equity position. It gives you a sense for what your maximum VaR and volatility are, and it allows you to compare unlevered returns to a typical long/short fund.